The invention relates to a portable power tool having a housing with a gearhead, having a motor shaft which can be rotationally driven by a motor and which can be coupled via an eccentric coupling drive to a tool spindle for the drive thereof, wherein the tool spindle can be driven in a rotational oscillatory manner about the longitudinal axis thereof and is designed for accommodating a tool.
Such a portable tool is known from WO 2008/128804 A1. This portable tool is a power tool having a drive unit for driving a drive shaft and an output shaft, on which a tool is accommodated. The rotary movement of the drive shaft can be transmitted to the drive shaft via an eccentric coupling device.
Such portable tools can be used, for instance, for the cutting or grinding of workpieces, wherein the oscillation movement of the tool can in principle make possible precise guidance at a high cutting or removal capacity.
It has been found that the use of such portable tools can be accompanied by vibration loads, which an operator can find to be annoying during prolonged use.
In this connection, WO 2008/128804 A1 proposes to provide a mass balance device for compensating for vibrations, said mass balance device performing a compensating movement opposed to the eccentric coupling movement produced by the eccentric coupling device.
It is thus possible in principle to reduce vibration loads, but the mass balance device involves increased construction cost and considerable extra weight. It has been found that the oscillating components of the eccentric coupling device, the output shaft coupled thereto and the oscillation tool fixed to the latter have a high mass and a considerable moment of inertia. For perceptible vibration compensation, these must accordingly be taken into account when designing the mass balance device and consequently give rise to an increased overall weight.
In view of this, it is a first object of the invention is to disclose a portable power tool comprising an oscillating drive, which can be operated ergonomically and with little fatigue.
It is a second object of the invention is to disclose a portable power tool comprising an oscillating drive, which can be operated at high performance.
It is a third object of the invention is to disclose a portable power tool comprising an oscillating drive having a simple a construction.
It is a forth object of the invention is to disclose a portable power tool comprising an oscillating drive which can be switched between different gears.
It is a fifth object of the invention is to disclose a portable power tool comprising an oscillating drive having low vibrations during operation.